linux-kernel - Re: [PATCH] powerpc/kasan: KASAN is not supported on RELOCATABLE && FSL

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Message-ID: <448c0af8be2247a780ed42bc401ff50c@huawei.com>
Date:   Sat, 30 Nov 2019 02:09:45 +0000
From:   shaolexi <shaolexi@...wei.com>
To:     Christophe Leroy <christophe.leroy@....fr>,
        "benh@...nel.crashing.org" <benh@...nel.crashing.org>,
        "paulus@...ba.org" <paulus@...ba.org>,
        "mpe@...erman.id.au" <mpe@...erman.id.au>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Wangkefeng (OS Kernel Lab)" <wangkefeng.wang@...wei.com>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "liucheng (G)" <liucheng32@...wei.com>,
        "zhangyi (F)" <yi.zhang@...wei.com>
Subject: Re: [PATCH] powerpc/kasan: KASAN is not supported on RELOCATABLE &&
 FSL_BOOKE

>Le 29/11/2019 à 08:46, Christophe Leroy a écrit :
>>
>>
>> Le 29/11/2019 à 08:04, Lexi Shao a écrit :
>>> CONFIG_RELOCATABLE and CONFIG_KASAN cannot be enabled at the same
>>> time on ppce500 fsl_booke. All functions called before
>>> kasan_early_init() should be disabled with kasan check. When
>>> CONFIG_RELOCATABLE is enabled on ppce500 fsl_booke, relocate_init()
>>> is called before kasan_early_init() which triggers kasan check and results in boot failure.
>>> Call trace and functions which triggers kasan check(*):
>>>    - _start
>>>     - set_ivor
>>>      - relocate_init(*)
>>>       - early_get_first_memblock_info(*)
>>>        - of_scan_flat_dt(*)
>>>     ...
>>>      - kasan_early_init
>>>
>>> Potential solutions could be 1. implement relocate_init and all its
>>> children function in a seperate file or 2. introduce a global
>>> vairable in KASAN, only enable KASAN check when init is done.
>>
>> Solution 1 seems uneasy. of_scan_flat_dt() and children are general
>> functions that can't be set aside.
>> Solution 2 would destroy performance, and would anyway not work with
>> inline instrumentation.
>>
>> Have you tried moving the call to kasan_early_init() before the call
>> of
>> relocate_init() ?
>
>I just tried it with QEMU, it works. I'll send a patch out soon.
>

Yes I tried but couldn't get it to work on a P1010. There might be conflict
somewhere else with my kernel config. Will keep on debugging.
Thanks for the prompt reply and trying it out on qemu.

Lexi

>
>
>> On other PPC32, kasan_early_init() is the first thing done after
>> activating the MMU. But AFAIU, MMU is always active on BOOKE though.
>>
>> Christophe
>>
>>>
>>> Disable KASAN when RELOCATABLE is selected on fsl_booke for now until
>>> it is supported.
>>>
>>> Signed-off-by: Lexi Shao <shaolexi@...wei.com>
>>> ---
>>>   arch/powerpc/Kconfig | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index
>>> 3e56c9c2f16e..14f3da63c088 100644
>>> --- a/arch/powerpc/Kconfig
>>> +++ b/arch/powerpc/Kconfig
>>> @@ -171,7 +171,7 @@ config PPC
>>>       select HAVE_ARCH_AUDITSYSCALL
>>>       select HAVE_ARCH_HUGE_VMAP        if PPC_BOOK3S_64 &&
>>> PPC_RADIX_MMU
>>>       select HAVE_ARCH_JUMP_LABEL
>>> -    select HAVE_ARCH_KASAN            if PPC32
>>> +    select HAVE_ARCH_KASAN            if PPC32 && !(RELOCATABLE &&
>>> FSL_BOOKE)
>>>       select HAVE_ARCH_KGDB
>>>       select HAVE_ARCH_MMAP_RND_BITS
>>>       select HAVE_ARCH_MMAP_RND_COMPAT_BITS    if COMPAT
>>>